It is well known in the prior art to employ dry pipe automatic sprinkler systems for control of fires. Such systems have air under pressure in the distribution pipes. A drop of pressure triggers the opening of a valve permitting the entry of water to the system. Since there is a possibility of leakage of air out of the system when no fire exists, it is known to employ a valve mechanism associated with each sprinkler head to prevent the discharge of water until such time as heat activates the sprinkler head. Such valves are also employed in pipes connecting sprinkler heads to distribution pipes filled with water where the distribution pipes are in a heated area and the sprinkler heads are located in an unheated area where freezing is possible. Such pendent pipes and sprinkler heads are conventionally referred to as pendent sprinkler assemblies.
The distribution pipes for sprinkler systems are generally installed a considerable period of time before the installation of the ceiling which is installed below such pipes. The general practice has been to install the pendent sprinkler assembly after the installation of the ceiling thus denying the structure the protection of the sprinkler system until the ceiling has been installed. To overcome this deficiency, vertically adjustable wet pipe pendent sprinkler assemblies have been developed as seen for example in U.S. Pat. Nos. 3,529,671, 3,675,952 and 3,807,503. Such an assembly can be installed at the same time that the distribution pipes are being installed and thus give the structure involved the protection of the sprinkler system well prior to the installation of the ceiling. Once the ceiling is installed, the assembly is vertically adjusted to position an escutcheon against the ceiling.
Dry pipe devices such as that disclosed in U.S. Pat. No. 4,007,878 and similar devices wherein threaded connections are employed for vertical adjustment in lieu of a collet are expensive since they require a special fitting to accommodate the upward and downward movement of the pendent tube and slidable plug assembly rather than having the latter assembly connect directly into a tee of the distribution system. They also require that the assembly be vertically offset from the distribution pipe as distinguished from the conventional assembly which lies in the same vertical plane as the distribution pipe.
The adjustable pendent sprinkler assembly of the invention eliminates the above discussed disadvantages of the prior art adjustable dry pipe pendent sprinkler assemblies.